The present invention relates to implantable medical devices for delivering a liquid therapeutic substance to a delivery site within a patient. More particularly, it relates to systems and methods for percutaneously locating one or more septum ports of the implantable medical device.
A variety of implantable medical devices are available for treating patients. For example, implantable substance delivery devices are typically used to deliver infusion media or therapeutic substances (such as medication) to a patient at a regulated dosage. The implantable substance delivery device (sometimes referred to as a drug pump) is implanted by a physician into a patient at a site appropriate for the therapy. Typically, an infusion catheter is connected to an outlet of the device, and is implanted/positioned to infuse the therapeutic substance at the desired therapy site so as to treat a condition such as pain, spasticity, cancer, neurodegenerative diseases, trauma, diabetes, or other medical conditions. The term “implantable substance delivery device” as used herein refers to any implantable device for delivering medicaments including, but not limited to, bladder pumps, accumulator pumps, fixed-rate bellows pumps, and the like, as well as implantable devices that do not necessarily include a pump.
In general terms, the implantable substance delivery device commonly includes a drug reservoir containing a volume of the infusion media, and a pump and/or metering mechanism to propel the infusion media in some metered or other desired flow dosage to the therapy site from the reservoir via the catheter. Over time, the therapeutic substance in the reservoir becomes depleted and it is necessary to refill the device with a new supply of therapeutic substance. In order to avoid surgically accessing and refilling the device, it is desirable to have the ability to percutaneously refill the drug reservoir. This is commonly done by providing the delivery device with a fill port assembly that includes a fill port establishing fluid access to the drug reservoir from an exterior of the device. In this regard, a resilient, resealable septum is provided with the fill port assembly, and is accessible by percutaneously inserting a hypodermic needle through the skin and then the septum via a fill port opening provided at the device's exterior. Once the septum has been pierced, the hypodermic needle is fluidly connected to the drug reservoir such that the reservoir can be refilled. Additional septum-type port assemblies can also be provided with the implantable device, such as a catheter access port assembly.
Because the device is implanted within the patient and cannot be seen directly, care must be taken to ensure that the needle is properly placed into the fill port assembly before transferring liquids. If the needle is not located within the fill port assembly (e.g., does not pass through the fill port opening; is mistakenly inserted into the catheter access port; the needle does not pierce the septum; etc.), delivery of the infusion media through the needle can result in immediate delivery of a significant quantity of the drug to the patient, with potentially adverse consequences. In addition, unintended failure to properly refill the drug reservoir may lead to complications for the patient when the needed medication is not dispensed at a later time. Other concerns may arise for a clinician intending to deliver liquids to and through the catheter access port; if the fill port is instead mistakenly accessed by the needle, an undesired liquid may be filled into the drug reservoir leading to potential complications.
In light of the above, efforts have been made to identify to the clinician a location of the fill port assembly (and/or the catheter access port assembly) relative to the patient's skin prior to insertion of the needle. For example, templates are well known, and can provide a general indication or map of the fill port and/or catheter access port location(s) following palpating the device's periphery through the patient's skin. Additionally, electronic and/or magnetic systems have been suggested that may provide the clinician with additional information generally indicative of the port assembly position. Due to the importance of accurately locating the desired port opening, any improvements in this area would be well-received. As implantable therapeutic substance devices become increasingly reduced in size, correctly locating the desired port assembly or opening has become increasingly more difficult as the ports are located in relatively close proximity to one another.
In light of the above, a need exists for improvements in percutaneously locating a port assembly of an implantable medical device.